Obtain 150 specimens of breast cyst fluid the first year; if distinctive variations are found in biochemical, hormonal, or immunological determinations, then obtain 350 breast cyst fluids the second year and 500 the third year. Analyze these breast cyst fluids for the following components: tumor associated antigens (CEA, TPA, a-Fetoprotein), chorionic gonadotropin, pituitary gonadotropin, minerals, protein nitrogenous constituents, DNA and polyamines, lipids, enzymes, and hormones as outlined in the original proposal. The hormone determinations will be performed by a subcontractor, the Institute for Steroid Research of Montefiore Hospital. Collect all initial clinical information and ongoing clinical follow-up on each patient. Follow-up women who have BCF aspirated and analyzed for at least five (5) years after aspiration to determine if they do or do not develop breast cancer. Provide biostatistical support for computer storage and statistical analysis of the above data.